PROJECT SUMMARY/ABSTRACT ? CORE B Allogenic hematopoietic stem cell transplant (allo-HCT) can provide a cure for chronic infections, genetic diseases, or cancers of the blood. However, its therapeutic utility is limited by associated toxicities resulting from graft versus host disease (GVHD). Among the most prominent morbidities of GVHD is damage to the gastrointestinal tract. Recent results from our groups have revealed that the severity of GVHD is impacted by the nature and metabolic properties of the gut microbiome. Further, we found that promotion of microbial communities that facilitate the metabolism of starch into butyrate and reprogram bile acid metabolism of the host ameliorate or even prevent GVDH following BMT. The measure and quantitation of metabolism is essential to address the associated experimental aims across the research proposals. The purpose of the Metabolomics core is to support the research projects that build on these studies to detect and quantify metabolites from these pathways in stool from mice, bacterial populations, human epithelial cells, and longitudinal stool samples of patients in the associated clinical trial. Further, this core will also provide global insights into host and microbiome metabolism using stable isotope tracing technologies and untargeted metabolome-wide profiling. By centralizing the development, maintenance, and implementation of metabolomics methods, this core will provide state-of-the-art capabilities to facilitate data collection and analysis while ensuring consistency across projects.